Photographic processes and lightsensitive elements therefor



'Dec. 21, 1948. E B KNOTT ET AL v 2,456,955

PHOTOGRAPHIdPRbCESSES AND LIGHT-SENSITIVE ELEMENTS -THEREFOR Filed Aug. 1, 1947 ,BLU,E akE /v RED I l L -C0L0UkEP ORIGINAL LAYER 0F EMULSION (RED sENs/TTvE) WHICH FORMS LATENTJMAGE MosTLr INSIDE THE s/L VEI? HAL/DE GRAINS LA YER 0F mun/01mm. JEHs/T/VE) wH/cH FORMS sukFAcE LA TENT lMAaE, THE EMULS/0N HAVING THE sAME GAMMA AS THE ABOVE EMULSION SUPPORT ExPasE TO LIGHTED COLOURED ORIGINAL SHOWN AT@ WITH RED LIGHT LAYLR' 0F EMULSION CONTAIN/N6 NEGATIVE LATC'N 7' IMAGE MOSTLY INS/DE 774E SILVER HAL/Pf GRAINS LAYER 0F EMULSION CONTAINING NEGATIVE LATENT IMAGE 0N SURFACE OF ERA/N5 SUPPORT DEVELOP m A Suki-A c: "COLOUR DEVELOPER co/vTA/iv/Na A COLOUR COUPLER GIVING A M/Hw BLUE-(mum) IMAGE LAYER 0E EMULs/o/v COMM/MING N664 m E LATE/vT IMAGE M0572) mm: THE s/L Vfl? HAL IDL' G/PA/NJ YELL 0w IMAGE FROM WHICH DEVELOPED s/L VEI? l5 SUBSEQUENTLY REMOVED SUPPORT DEVELOP IN AN "INTERNAL" COLOUR DEVELOPER CONTAINING A COLOUR COUPLER e/w/vc; A

MINUS GKEINKMAGENTA) IMAGE MAGENTA IMAGE FROM WHICH DEVELOPED 2%?? 5/1. TE 1: suasEouEurLY REMOVED 44 Q5) YELLow IMAGE FROM WHICH DEVELOPED J/LVER 1s SUBSEQUENTLY REMOVED k EDWARD BOWES KNOTT JUPPORT GUY WILLIAM wmus STEVENS INVlENTOR-S 71-72 F /WM ATTO EYS Patented Dec. 21, 1943 I 2,456,955

UNITED STATES. PATENT? OFEFICEJ,

PHBTOGRAPHIG PROCESSES'AND LIGHT SENSITIVE ELENIENFIS' THEREFOR Application August 1, 1947, Serial No. 765 634 In Great Britain June 2; 1944 1 12.Claim's.:(Cl 95 v r 1 H 2 This invention relates to photographic procin essessand 'materia'ls therefor. This invention 13 v v y n V I a modification'of thatdescribed and claimed in INTERNALDEVELOPER' our copending application SerialNo. 765,636, filed Hydroquinong m 15 d August 1, 1947. In said application Serial No. 5 N..met,hy1-p-aminopheno1 ,su1phate do 15 765,636, *wehave 'describedcertain methods and sodium su1phite, anhy adorn" 50 materials-using twodifferent kindsof silver Salt Potassium bromide dol 10 emulsions, designated therein as emulsions of Sodium hydroxide do type I and emulsions of type :II, so constituted Sodium thiosulphate .(cryst) do 20. and arranged on a single supportthat each of *Watersto: l ccs;' .l0fl0 them can be selectivelyexposed, and"themodifi Development time'3: minutes at 20C. cation'in which this requirement regarding selec.-, FORMULA xnflwfl t1ve exposure can be dispensed with m Wl'llCh case I the emulsions have differing gammas.

Wehave now found that said requirement can. PM '"Hydroquinone g1:am5 H 12 be dispensed with even when the emulsions give N ethyl- -aminophenol. sulphate do 3 the same gamma. Sodiumsulphite (cryst) do 90 The present invention provides the method of Potassiurri..bromide do 4 producing a photographic image of an: object or Sodium carbonatelcrystl) do i .150. image wherein a light-sensitive material compris'-- Sodium.thiosulphate..(cnyst...) do 20 ing a silver salt-emulsion of type 'I' and a silver Water,rt0- ccs a1.00.0 salt emulsion of type II, both of the'same gamma 2 Development timelel. minutes at 2010. .1 and coated either as superimposed layers or FORMUMLIH: m1xed,-1. e.,insep-arably combined and extendingg v N over the same areaon a single supportis exposed CQMMERCIALDEVELOPERm o s li h j t 01' ima ther by xpo ng This'is the:S3.me'a-S-1F01mu1a Ii (b) but .omitboth emulsions simultaneously, 'andzthe exposed tingithe tsodium:,thiosulphate.-.1:. material is developed first in a surface" developer Formula II (a) is a more energeticdeveloper 1 and then in an internal developer. than; Formula- :11 3.61)) ssolthat zit usually gives-1a Type I emulsions are thos which upon e p-gghighen'effective speed andahigher contrastvthans ure to light'form the latent image mostly inside Formula II (-b) rbut-zuis :often=;notso-convenient; t silver salt grains -These emmsions after since it has a; highertendency-to aerial oxidation posure to light canbe developed in internal" -Q give developers. Type II emulsions are those which 35. m fi described" upon exposure to light form surface latent image? Ounflnvemlon" partly-5m Yregardto theory1 0f internaliandr surface datentsimages,z-xtheacorrecte nessr or .nthenwise; of such;theory,--v is not essential to the successful working of the invention; it 'oe-m ing only: necessary to "choose .t-the;.lemulsions ace cordin'gztto cthei'tests: hereinafter; :given-d .xz,

Thet'zpresent inventionan'employs:"the following. 1

Theseemulsions after-exposure to light'can .be developed in either-internal or stir-face (level opers.

Developers for developing such latentimages 40 are as follows 2' 1 I typfisof I}. M

SURFACEQVDEVELOPER These are,the 8111111510118,W1'liGh".Wi1l' develop I (after exposure to light)ttin internalrdevelopers' p'fiydri'iyphenylglycme 10 of the. .kind given" in at TIESISUJDHH'Of Formulae Sodmm Barbonate (Myst) II (a) .and II *(b); but will "not developer only Watentou I slightly'fdevelop'inFormula'fIII'or in Formula I,

pment timeg minutes. at 209.0. .50 i. e., theisurfac'e dBVBIODElSLL'LT (1) Normal range of exposures As measured according to normal photographic testing technique, when a test layer of the type I emulsion is coated on a transparent support (e .'g'. glass) and the layer is exposed to a light intensity scale the whole of which is exposed for some fixed time between /100 and 1 second and is developed in the internal developer II (a) the trans mitted density obtained at any point along the logioE axis over a density range of 3.0,starting from the threshold of the curve (D=0.1 above fog) should be at least 5 times, and preferably at least times the transmitted density obtained when an identical test layer of the emulsion is developed with the surface developer of Formula Gamma can be measured as set forth in British Patent 541,510 and as used herein means the average slope of the characteristic H and D curve I or preferably III, the measurements of density (2) Small range of exposures For this purpose the emulsion need not conform to such a rigid requirement, for instance for making a tone correcting mask, but it is suificient if in the above test the upper limit of 3.1 is substituted by an upper limit of 1.0.

TYPE II These are the emulsions which when exposed to a light intensity scale, the whole of which is exposed for some fixed time between fl th and 1 second, will develop normally in Formulae I and III as well as in Formulae II (a) and II (b). As measured according to normal photographic testing technique, when a test layer of the emulsion is coated on a transparent support (e. g. glass) and the layer is exposed to a light intensity scale the whole of which is exposed for some fixed time between $4100 and 1 second and is developed in the internal developer II (b), the transmitted density obtained at any point along the 10g10E axis of the curve between the density range of 0 to 3.0, preferably 0 to 2.0, does not exceed the transmitted density obtained when an identical test layer of the emulsion is developed in Formula III, the measurements of density being made at the same points on the logioE axis of the curve.

Since Formula III contains sodium sulphite and Formula I is free from sulphite, and sulphite is known to have some solvent action on silver chloride and bromide (although very little on silver iodide), it is apparent that when making any of the above measurements on an emulsion to obtain, with a high degree of precision, in-.

formation on the amount of surface latentimage given by such emulsion, it is important-to use.

better density in the image produced by the development of the type II emulsion.

It is to be noted that an internal developer is necessarily capable of developing not only a latent image inside grains but also of developing a latent image on the surface of grains (Whether between the densities of 0.4 to 1.6. In measuring gamma, development is done at 68 F. for 1 minutes in the following solution:

N-methyl-p-aminophenol sulphate grams 2.2 Sodium thiosulphate, crystals do 150.0 Hydroquinone do 17.0 Sodium carbonate, crystals do 175.0 Potassium bromide do 2.8 Water to ccs 1000 ;or vice versa, or both developers may be colour developers, for example if one developer gives a yellow coloured image and the other developer gives a cyan (blue-green) coloured image, the finished result will be of green colour and the amount of yellow and the amount of cyan can be "conveniently controlled to give any particular shade of green desired, from a very yellowish coloured green to a rather bluish coloured green.

This kind of material is useful in the production of coloured masks for use in colour photographic reproduction where it is desired that the coloured mask should comprise two superimposed images being records of the same colour sensation but of different colours; coloured masks which comprise such images and their use have been described in British Patent No. 568, i l0. For instance, the material according to the present invention can be made with emulsions both sensitive to red light and after exposure to a multi-coloured original, the one emulsion can be developed with a surface developer containing a colour coupler giving a minus blue (yellow) image and then the other emulsion with an internal developer containing a colour coupler giving a minus green (magenta) image, the developed silver being subsequently removed in the usual way. When such a combined image is used as a mask in reproducing said original, the minus blue image compensates for the undesired absorption of blue light by the cyan (blue-green) image in the original or in the reproduction or both; similarly the minus green image compensates for the undesired absorption of green light by the cyan image in the original or in the reproduction or both. Similarly both the layers may have a colour sensitivity other than red and developed to other colours just as for the two layers described in British Patent No. 568, l40. Although this method of making a mask in two colours involves two development steps it has the advantage over methods involving only one step that the development of each colour can beseparately watched and controlled so as to give more easily and exactly the relative depths of colours required. Moreover the two emulsions can with advantage be coated as a mixture in a single layer. 7

The accompanying drawing shows a flow-diagram which depicts graphically one embodiment of our invention, viz. the production of a coloured mask as described above. At B is shown a support coated with a red sensitive layer of photographic silver halide emulsion which forms surface latent image and coated on such first emulsi on layer, a red sensitive layer of photographic silver halide emulsion which forms latent image mostly inside the silver halide grains, both emulsion layers having the same gamma. Upon exposing this sensitive element to the coloured original shown at A with red light, negative latent image corresponding to the red portion of the coloured original is formed in both emulsion layers as shown to C. Upon developing the whole element in a surface colour developer containing a colour coupler giving a minus blue (yellow) image, the upper emulsion layer which contains internal latent image is not developed, while yellow image (from which developed silver is subsequently removed) is formed in the lower emulsion layer as shown at D. Upon developing the element in .an internal colour developer containing a colour coupler giving a minus green (magenta) image, magenta image (from which developed silver is subsequently removed) is formed in the upper emulsion layer, as shown at E, thus providing a coloured mask which can be used in reproducing said original.

As another illustration the invention is also useful in the production of motion picture sound films, that is to say films having a series of pictures and also a sound track alongside the pictures. In some methods of sound recording and reproduction it is desirable that the gamma of the sound should be lower than that of the pictures. If the material of the present invention is exposed to produce therein latent images of pictures and sound track (side by side) then both can be first developed in a surface developer whereafter the picture areas only can be developed further in an internal developer by roller application of such developer to such areas only; Then the film is fixed and washed in the usual way. This will give a greater gamma in the picture areas than in the sound track.

In the present invention the two emulsions may or may not have the same speed according to the results desired or the purpose for which it is to be used. This applies for instance to the two illustrations given above. When the emulsions have different speeds as measured by the exposure which gives a density of 0.2 when developed in the surface and internal developers referred to above, the material can be used to give a convenient control of the strength of the developed image when the proper exposure is difficult to determine with accuracy. For instance the speed of the type I emulsion can be made greater (say three or five times) than that of the type II emulsion. Such a material can be used for exposure in a camera (or otherwise) and is so exposed for a time which is estimated (by guesswork) to be correct for the type II emulsion. The exposed material is then immersed in a surface developer. If the estimate was in fact satisfactory, then the surface developer will produce a satisfactory image, but if the estimate was only say one third that of the correct exposure for the type II emulsion then little or no image will olevelop therein, and in this case the material can t e be. mmersed .ican internal? developer wherein the Type I emulsion will develop to give an image, which is at least more satisfactory.

Alternatively the type II emulsion can be of greater speed (say five times) than the type I and again first developed in a surface developer; in this case if the first developed image in the type II emulsion is unsatisfactory, namely overexposed, it can be bleached out by a silver removing bath (e. g. a bichromate bath) and then the image in the type I emulsion can be developed by means of an internal developer. This is useful in the case of camera exposures where the lighting conditions are such that the operator may tend to err on the overexposure side.

The preparation of emulsions of type I and type II is described in our copending application Serial No. 765,636, filed August 1, 1947 except it should here be pointed out that there is no great di fliculty in making the two emulsions so as to give the same gamma in the sense stated above, for instance an easy way is first to make a type I emulsion of about the desired gamma, then ascertain its gamma accurately, and finally prepare a type II emulsion which during its preparation can be tested and adjusted as is commonly .done in the art until it has the same gamma as the type I.

The preparation of developers, including colour developers suitable for developing type I and type II emulsions is described in our copending application Serial No. 765,636, filed August 1, 1947.

This application is a continuation-in-part of our copending application Serial No. 589,095, filed April 18, 1945.

What we claim as our invention and desire to be secured by Letters Patent of the United States is:

1. The method of selectively producing photographic images in a photographic material containing, inseparably combined and extending over the same area on a sigle support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver salt photographic emulsion (I) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between and 1 second and development for 8 minutes at 20 C. in the following developer (IIa) Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do 10 Potassium bromide do 10 Sodium hydroxide "dos--- 25 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logioE axis, over a range of 1.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C, in the following developer (I) p-I-Iydroxyphenylglycine grams 10 Sodium carbonate, crystals do' 100 Water to ccs 1000 the measurements of density being made at the same points on the logmE axis, and the other of said emulsions being a light-sensitive silver salt photographic emulsion (II) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between /100 and 1 second and development for 4 minutes at 20 C. in the following developer (IIb) Hydroquinone grams 12 N-methyl-p-aminophenol sulphate -do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logmE axis of the curve between the range of to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III) Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate do 150 Water to ccs 1000 the measurements of density being made at the same points on the logmE axis of the curve, comprising simultaneously exposing the aforesaid emulsions to a lighted object or image, then treating the whole material with a developer which develops substantially only the latent image which is developable by developer (III) and then developing the whole material in a developer which develops the latent image which is developable by developerflla) 2. The method of selectively producing photographic images in a photographic material containing, inseparately combined and extending over the same area on a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver salt photographic emulsion (I) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between and 1 second and development for 3 minutes at 20 C. in the following developer (Ila):

Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do 10 Potassium bromide do 10 Sodium hydroxide do 25 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logioE axis, over a range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer p-Hydroxyphenylglycine "grams" Sodium carbonate, crystals do 100 Water to ccs 1000 the measurements of density being made at the same points on the logmE axis, and the other of said emulsions being a light-sensitive silver salt photographic emulsion (II) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between /100 and 1 second and development for 4 minutes at 20 C. in the following developer (IIb):

8 Hydroquin-one grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide do 4 Sodium carbonate, crystals do r 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logmE axis of the curve between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III):

Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate do 150 Water to ccs .1000

the measurements of density being made at the same points on the logmE axis of the curve, comprising simultaneously exposing the aforesaid emulsions to a lighted object or image, then treating the whole material with a developer which develops substantially only the latent image which is developable by developer (III) and then developing the whole material in a developer which develops the latent image which is developable by developer (Ila).

3. The method of selectively producing photographic images in a photographic material containing, inseparably combined and extending over the same area on a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver halide photographic emulsion (I) a test layer of which coated on a transparent glass sup port upon exposure to a light intensity scale for a fixed time between 1 and 1 second and de-. velopment for 3 minutes at 20 C. in the following developer (IIa):

Hydroquin one grams l5 N-methyl-p-aminophenol su1phate do I 15 Sodium sulphite, anhydrous do 10 Potassium bromide do 10 Sodium hydroxide do 25 Sodium thiosulphate, crystals do Water to ccs 1000 gives a transmitted density at any point along the logmlil axis, over a range of 3.0 starting from the threshold of the characteristiccurve beginning at density of 0.1 above fog, at least 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (I):

p-Hydroxyphenylglycine grams 10 Sodium carbonate, crystals do Water to ccs 1000 Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide -do 1 4 Sodium carbonate, crystals 'grams 1'50 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the loginE axis of the curve between the range of to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III):

I-Iydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90, Potassium bromide do 4 Sodium carbonate do 150 Water to ccs 1000 the measurements of density being made at the same points on the logioE; axis of the curve, comprising simultaneously exposing the aforesaid emulsions to a lighted object or image, then treating the whole material with a delevoper which develops substantially only the latent image which is develo-pable by developer (III) and then developing the whole material in. a developer which develops the latent image which is developable by developer (11a).

4. The method of selectively producing photographic images in a photographic material con taining, inseparably combined and extending over the same area on a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver halide photographic emulsion (I) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between l ioo' and 1 second and development for 3 minutes at 20 C. in'the followingdeveloper (IIa) gives a transmitted density at any point along the logioE axis, over a range of 3.0 'startingjfrom the threshold of the characteristic curve begin ning at a density of 0.1 above fog, at least times the transmitted.density'obtained when an:

identical. test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer" p iiydroxyphenylglycine grams; 10": Sodium carbonate, crystals do 100: Water to ccs 1000 the measurements of densityj beinig maclle at the"v same points on the logioE axis, and the other of said emulsions b i a l tensi i lv r a id photographic emulsion (II) a test layer of which coated on a transparent lass support upon'exposure to a light intensity scale for a fixed'time between V100 and'l second and developm entfor i minutes at 20 C. in the following developer (Kb) 2 I-Iydroquinone; grams N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 P'otassiumbromi'de do g Sodium-"carbonate; crystals do; 150' Sodium thiosulphate, crystals do; 20 Water to ccs'i; 1000' T0 gives'a' transmitted" density at any point along the logm'E axis of the curve between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4' minutes at 20 C. in the'follow'ing developer (III) Hydroguinone; 1 ;grams 12 N-inethyl-p-a'minophenol s'ulphat'e do 3 Sodium sulphite; crystals' do 90 otass m bromide 'do 4 Sodium carbonatedo 150 Water to ccs 1000 the measurements. of density being made at the same points on' the logioE axis of the curve, compris'ihgsimultaneously exposing the aforesaid emulsions to a lighted object or image, then treating the Whole material with a developer'- which develops substantially only the latent image 'whicli'i's develop'able by developer (III) and then developing the whole material, in a developer which develops the latent image which is devel-opable" by developer (IIa).

5. The'methodof selectively producing photographic'images in a" photographic material containing,inseparably combined and extending over the same area. on a single support, two photographic emulsions'having the same gamma, one of said" emulsions being a light-sensitive silver halide photographic emulsion (I) atest layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time betwee'n- /1dd and; 1' second and development for 4 minutes" a't'20" C. in the followingdevelope'r' (IIb):

Hydroquinone grams 12. N-methyl-peaminophenol sulphate do 3 S dium .sulph ta. cr l d0 90 Potassium"hroinidmpgdo; 4 Sodium carbo ate;' crystals; do 150 Sodiumthiosulphate; crystals" do 20' Water tbi ccs 1000 gives a transmitted density at any point along the logmEaxis, over a range of 3.0 starting from the threshold of the'characteristic curve beginning at a density of 0.1 above fog, at least 5 times the transmitted; density obtained when an identical testlayer of the-emulsion is developed for 4 minutes at 20 C. in the following developer (III) Hydr'oquinone r grams 12 N-methyl-p-amin'o'pheiiol sulphate do 3 Sodium isulphite, crystals do 90 Potassiumbromide:- do 4 Sodium carbonate; crystals' do 150 Water to- -1 ccs' 1000 the measurements of; density being made at the,-

sa'm''points" onthe IOgIOE axis, and the other of said emulsions being a light-sensitive silver halide emulsion (II) a test layer of which coated on a transparentglass support upon exposure to a light intensity scale for a fixed time between V1 and .1.. sec.ond and development for 4 mindensityobtained when an identical test layer of the emulsion (II) is'developed for 4 minutes at 20 C. in the aforesaid developer (III), the measurements of density being made at the same points on the logiolii axis of thecurve, comprising simultaneously" exposing the aforesaid emulsions,

to a lighted object or image, then treating the whole material with; a developer which develops "'11 substantially only the latent image which is developable by developer III and then developing the Whole material in a developer which develops the latent image which is developable by developer (IIa).

6. The method of selectively producing photographic images in a photographic material containing, inseparab-ly combined and extending over the same area, on a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver halide photographic emulsion (I) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between o and 1 second and development for 4 minutes at 20 C. in the following developer (IIb) Hydroquinone grams 12 N-m-ethyl-paminophenol sulphate -do--- 3 Sodium sulphite, crystals -do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 ives a transmitted density at any point along the logioE axis, over a range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least 10 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in thefollowing developer (III) Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide 'do .4 Sodium carbonate, crystals do .150 Water to -I 'ccs 1000 the measurements of density being made at the same points on the logioE axis, and the other of said emulsions being a light-sensitive silver halide emulsion (II) a test layer of which coated on a transparent glass support upon exposure to alight intensity scale for a fixed time between A o and 1 second and'development for 4 minutes 'at'20" C. in the aforesaid developer (IIb) gives a transmitted density at any point along the lOglOE axis of the curve between the range of 0 and 2.0 which does notexceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the aforesaid developer (III) the measurements of density being made at the same points on the logmE axis of the curve, comprising simultaneously exposing the aforesaid emulsionsltoa lighted object or image, then treating the whole material With a developer which develops substantially only the atent image which is 'developable by developer (III) and then developing the whole material in a developer which develops the latent image which is developable by developer (IIa).

7. A photographic material containing, inseparably combined and extending over the same,

area on' a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver salt photographic emulsion (I) a test layer of which coated on a transparent glasssupport upon exposure to a light intensity scale for a fixed time between i o and 1 second and development for 3 minutes at 20 C. in the following developer (IIa) Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do 10 Potassium bromide do 10 12 Sodium hydroxide grams 25 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logioE axis, over a range of 1.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (I) p-I-Iydroxyphenylglycine grams 10 Sodium carbonate, crystals do 100 Water to ccs 1000 the measurements of density being made at the same points on the logioE axis, and the other of said emulsions being a light-sensitive silver salt photographi emulsion (II) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between o and 1 second and development for 4 minutes at 20 C. in the following developer (IIb) Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to -ccs 1000 gives a transmitted density at any point along the logmE axis of the curve between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developedfor 4 minutes at 20 C. in the following developer (III) Hydroqulnone "grams" 12 N-methyl-p-aminophenol sulphate d-o 3 Sodium sulphite, crystals do 90 Potassium bromide do- 4 Sodium carbonate -do 150 Water to ccs 1000 the measurements of density being made at the same points on the logioE axis of the curve.

8. A photographic material containing, inseparably combined and extending over the same area on a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver salt photographic emulsion (I) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between tio and 1 second and development for 3 minutes at 20 C. in the following developer (IIa) Hydroquinone grams 15 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do 10 Potassium bromide do 10 Sodium hydroxide do 25 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logioE axis, over a range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (I) p-Hydroxyphenylglycine grams 10 Sodium carbonate, crystals do Water to ccs 1000 the measurements of density bein made at the same points on the, logmE axis, and the other of said emulsions being a light-sensitive silver salt photographic emulsion (II) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between and 1 second and development for 4 minutes at 20 C. in the following developer (IIb):

Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals. do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logmE axis of the curve between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C.

in the following developer (III):

Hydroquinone grams 12 N -methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate do 150 Water to ccs 1000 the measurements of density being made at the same points on the logmE' axis of the curve.

9. A photographic material containing, inseparably combined and extending over the same area on a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver halide photographic emulsion (I) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between A00 and 1 second and development for 3 minutes at 20 C. in the following developer (Ila):

Hydroquinone grams- 15 N-methyl-p-aminophenyl' sulphate do 15 Sodium sulphite, anhydrous; do 10 Potassium bromide do 10 Sodium hydroxide do 25 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the IOglOE axis, over a range of 3.0 starting from t the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. inthe following developer (I) p-Hydroxyphenylglycine grams Sodium carbonate, crystals do 100 Water to -ccs 1000 the measurements of density being made at the same points on the IOgIOE axis, and the other of said emulsions being a light-sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between /1 and 1 second and development for 4 minutes at 20 C. in the following developer (IIb) Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density" at any point along the logmE axis of the curve between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III) Hydroquinone grams 12 N-methyl-p-aminophenol su1phate do 3 Sodium sulphite, crystals l do Potassium bromide do 4 Sodium carbonate do 150 Water to ccs 1000 Hydroquinone grams 1'5 N-methyl-p-aminophenol sulphate do 15 Sodium sulphite, anhydrous do 10 Potassium bromide do- 10 Sodium hydroxide do 25 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logioE axis, over a range of 3.0- starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least 1-0 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C-. in the following developer (I):

p-I-Iydroxyphenylglycine grams 10 Sodium carbonate, crystals do Water to ccs 1000 the measurements of density being made at the same points on the logmE axis, and the other of said emulsions being a light-sensitive silver halide photographic emulsion (II) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between 50 and 1 second and development for 4 minutes at 20 C. in the following developer (IIb):

Hydroquinone "grams" 12' N-methyl-p aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate, crystals do Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logmE' axis of the curve between the range of 0 to 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the following developer (III):

Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate do 150 Water to ccs 1000 Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logmE axis, over a range of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least 5 times the transmitted density obtained when an identical test layer of the emulsion is developed for 4 minutes at 20 C. in the following developer (III):

Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do 90 Potassium bromide do 4 Sodium carbonate, crystals do 150 Water to ccs 1000 the measurements of density being made at the same points on the IOgIUE axis, and the other of said emulsions being a light-sensitive silver halide emulsion (II) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time be tween A00 and 1 second and development for 4 minutes at 20 C. in the aforesaid developer (IIb) gives a transmitted density at any point along the logmE axis of the curve between the range of 0 and 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the aforesaid developer (III), the measurements of density being made at the same points on the logmE axis of the curve.

12. A photographic material containing, inseparably combined and extending over the same area on a single support, two photographic emulsions having the same gamma, one of said emulsions being a light-sensitive silver halide photographic emulsion (I) a test layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between /100 and 1 second and development for 4 minutes at 20 C. in the following developer (IIb):

I-Iydroquinone "grams" 12 N-methyl-p-arninophenol sulphate do 3 Sodium 'sulphite, crystals do 90 16 Potassium bromide "grams" 4 Sodium carbonate, crystals do 150 Sodium thiosulphate, crystals do 20 Water to ccs 1000 gives a transmitted density at any point along the logioE axis, over arange of 3.0 starting from the threshold of the characteristic curve beginning at a density of 0.1 above fog, at least. '10 times the transmitted density obtained when an identical test layerof the emulsion is developed for 4 minutes at 20 C. in the following developer (III):

Hydroquinone grams 12 N-methyl-p-aminophenol sulphate do 3 Sodium sulphite, crystals do Potassium bromide do 4 Sodium carbonate, crystals do 150 Water to ccs -1000 the measurements of density being made at the same points on the logmE axis, and the other of said emulsions being a light-sensitive silver halide emulsion (II) a test'layer of which coated on a transparent glass support upon exposure to a light intensity scale for a fixed time between Am and 1 second and development for 4 minutes at 20 C. in the aforesaid developer (IIb) gives a transmitted density at any point along the logmE axis of the curve between the range of 0 and 2.0 which does not exceed the transmitted density obtained when an identical test layer of the emulsion (II) is developed for 4 minutes at 20 C. in the aforesaid developer (III), the measurements of density being made at the same points on the 10gl0E axis of the curve.

EDWARD BOWES KNOTT. GUY WILLIAM WILLIS STEVENS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,857,083 Harris May 3, 1932 1,930,141 Capstaif Oct. 10, 1933 1,956,230 Schmidt Apr. 24, 1934 2,029,946 Schmid Feb. 4, 1936 2,197,994 Butement Apr. 23, 1940 OTHER REFERENCES Mees, The Theory of the Photographic Process, published 1942 by The MacMillan Co., New York; pages 150-152, 166-171, 196, 294-297 and 301.

Bullock, Chemical Reactions of The Photographic Latent Image, vol. I, published by Eastman Kodak 00., Rochester, New York, 1927; pages 15, 20, 22, 28, 30, 31, 47, 48, 50, 52, 72, 73, 80-85.

Wall, Photographic Emulsions, published by Amer. Phot. Pub. C0., Boston, 1929, pages 52, 53 and to137. 

